The International Telecommunication Union (ITU) Working Party 2 (WP2) of Study Group 16 (SG16) has developed and promulgated widely accepted standards for multimedia protocols for systems/terminals/application, for example, H.323, H.310, H.324. H.323 provides the real-time multimedia (audio, video, and/or data [text, still images and/or graphics]) communications over packet-based networks (e.g., Internet/Internet Protocol [IP], Asynchronous Transfer Mode [ATM], and Frame Relay [FR]). H.310 provides the real-time multimedia (audio, video, and/or data [text, still images and/or graphics]) communications optimized over the Asynchronous Transfer Mode (ATM) network only. H.324 provides the real-time multimedia (audio, video, and/or data [text, still images and/or graphics]) communications over the circuit-switched network line Public Switched Telephone Network (PSTN). These multimedia applications use common audio (G-series) and video (H-series) codecs as well as data (T-12x series) protocol standards.
In addition to the above-identified multimedia protocols, WP2 of SG16 (WP2/16) has developed a common control standard, Control Protocol for Multimedia Communication, which is also known as H.245. The H.245 control protocol is an end-to-end protocol and is used by all multimedia application protocols (including, for example, H.323, H.31 0, H.324), and others for controlling media, for example, audio, video, and/or data (such as text, still images, and/or graphics) between, user terminals.
However, H.323, H.310, H.324 and other multimedia protocol systems/terminals/applications often need additional value-added services to enable communications between users on the system. These value-added services can include, for example, Policy, Security, Directory, Billing/Accounting, Visitor/Home Location Functions, and others, and can be implemented as front-end services (FES) and/or as backend services (BES). In general, the above value-added services are implemented as BES and are used to provide information and resources necessary for call completion. An example of a common front-end protocol is a H.245 protocol standard, which was developed to be used with all of the above listed multimedia protocol systems/terminals/applications.
The characteristic control functions performed by the H.245 protocol can be summarized as follows:
Master-slave determination;Capability exchange;Bi-directional logical channel signaling;Mode request;Round trip delay determination;Maintenance loop detection; andSpecific user commands and indications.Because these characteristic control functions are common to all applications, H.245 was developed as a common control protocol for all of the applications without making it application-specific. This design characteristic has provided a very efficient and solid common foundation for the optimization of resources for both equipment manufacturers and service providers. As a result, separate control and services protocols do not need to be provided for each application.
Although each multimedia application protocol, for example, H.323, H.310, or H.324, has been standardized, each of these protocol use a unique protocol for requesting and communicating with the servers providing the value-added services. Specifically, functional entities, such as, multi-point controllers (MCUs), gateways (GWs), media gateway controllers (MGCs), and/or gatekeepers (GKs) operating using a given multimedia application protocol communicate with each other and the value-added service servers using a unique protocol known as an application-specific protocol. For example, the H.323 system uses its own H.323 protocol to communicate with its own terminals, GKs, MCUs, GWs, and MGCs. The same is the case for the H.310, H.324 and other multimedia application protocols. Unfortunately, none of these application-specific protocols are compatible with each other.
Similarly, since each application may need additional value-added services such as Policy, Security, Directory, Billing/Accounting, Visitor/Home Location Functions, and others, separate application-specific communication protocols are currently required for each multimedia application protocol to request and communicate with the value-added services. Fortunately, since these services are generally provided as application layer value-added services, the services do not need to be application-specific and, thus, can be implemented as common functions that are directly accessible by all application protocols using a common communication protocol.
Therefore, the development of non-application-specific common communication protocols that can be used by all multimedia application protocols to support each value-added service would be desirable.